Jafar Ramadhan Mohammed

An Improved Median Filter Based on Efficient Noise Detection for High Quality Image Restoration

To restore images corrupted by impulse noise, various image filtering strategies have been proposed. However, a common drawback of these methods is that the details and edges can not recovered satisfactorily when the noise level is high. A novel method based on efficient noise detection algorithm is proposed in this paper for effectively denoising extremely corrupted images and better details and edges preservation. The proposed method replaces only noisy pixel by either the median value or by a noise-free pixel value inside the selected filtering window. While uncorrupted pixels are remain unchanged. The key feature of the proposed method is very high noise detection accuracy, yielding zero miss-detection rate. Comparative studies of the proposed method and other methods for different images are made and the advantages of the proposed method are fully demonstrated.

A New Simple Adaptive Noise Cancellation Scheme Based On ALE and NLMS Filter

Background noise is usually an important factor that affects speech recognition performance and many other applications. In this paper, background noise (wideband noise and sinusoidal noise) can be significantly suppressed using the proposed adaptive noise cancellation scheme based on adaptive line enhancer (ALE) and normalized least mean square (NLMS) filters. The proposed scheme is comprised of two stages. The first stage uses an ALE filters, which are used to reduce sinusoidal noise from the primary and reference input signals, whereas the wideband noise is reduced using NLMS adaptive filter in the second stage. To demonstrate the effectiveness of the proposed scheme ,it is compared to the traditional adaptive noise cancellation scheme. The good performance of the proposed scheme have been verified via computer simulations in noisy and reverberant environment.

A New Technique for Obtaining Wide-Angular Nulling in the Sum and Difference Patterns of Monopulse Antenna

A simple technique for obtaining wide-angular nulling in the sum and difference patterns of the monopulse antenna is presented. This technique involves the addition of two elements, one at each end of the monopulse antenna array, which together produce a cosine pattern used for obtaining wide-angular nulls. By adjusting the amplitude of the excitation of the two-element auxiliary array, it is possible to modify the overall array pattern to place wide angular nulls in the directions of undesired interference signals.

An Efficient RLS Algorithm For Output-Error Adaptive IIR Filtering And Its Application To Acoustic Echo Cancellation

In this letter, an efficient recursive least squares (RLS) algorithm using infinite impulse response (IIR) filter for acoustic echo cancellation (AEC) is proposed. The RLS adaptive filter is naturally extended from the finite impulse response (FIR) structure to the IIR structure. One of the main advantages of an IIR RLS filter is that a long-delay echo can be synthesized by a relatively small number of filter coefficients leading to lesser computational complexity. In addition it is more suitable for modeling physical systems, due to its pole-zero structure, over their FIR counterparts. To investigate the tracking performance and the stability of the proposed IIR RLS filter in a practical implementation, real data for far end speech signal and its echo were used in car environment. The proposed algorithm is shown to have global convergence. To demonstrate the effectiveness of the proposed IIR RLS filter, it is compared to the usual FIR RLS filter. The good performance of the proposed IIR RLS algorithm for AEC have been verified via computer simulations

Sidelobe Cancellation for Uniformly Excited Planar Array Antennas by Controlling the Side Elements

A sidelobe cancellation over a wide angular range for the uniformly excited planar array is proposed. The approach is to readjust the amplitude and phase excitations of the boundary elements only, while keeping the rest of elements unchanged. Simple expressions for computing the required amplitude and phase excitations of these boundary elements are given. The technique simplifies the feed network as it requires only one attenuator and two phase shifters. Simulation results show that cancellation of sidelobes across a wide angle can be obtained.

A new robust adaptive beamformer for enhancing speech corrupted with colored noise

In this paper, a new adaptive beamforming scheme is proposed for enhancing a speech signal degraded by additive colored noise signals in reverberant environment. The good performance of the standard GSC beamformer is severely impaired in complicated acoustic environments. The proposed beamformer uses a new adaptive blocking matrix, which consists of linear prediction error filters (LPEFs) and a multi-channel noise canceller using adaptive noise estimation filters (ANEFs). The new adaptive blocking matrix exploits the stationary characteristics of the speech signal over a short interval of time. Thus most of speech signal can be predicted by the linear prediction filters in the blocking matrix. On the other hand, the background noise signals becomes white. While the ANEFs in the multi-channel noise canceller reconstructs the background noise signals from whitened noise signals. Simulation results, in a noisy and reverberant environment with 0.3s reverberation time, show that the proposed beamformer produces results that are significantly favorable than standard GSC beamformer. Moreover, the proposed beamformer has been implemented in a real-time in a real environment using National Instruments NI-PXI-1042Q controller system and data acquisition card PXI-4472.

Performance of a Wide Angle and Wide Band Nulling Method for Phased Arrays

In most practical applications of the phased array antennas, the generated nulls toward the interfering signals should have enough depth and width to accommodate ∞uctuations in frequency and direction of the interferer. Due to these ∞uctuations, the nulls can be easily deviated from its desired angular locations in the traditional adaptive nulling arrays since the nulls are very sharp and sensitive. An innovative technique for wide nulling arrays has been recently presented. The wide nulls can be introduced by setting properly the excitation coe-cients of the two edge elements of the antenna array. In this paper, the efiect of frequency ∞uctuation on the nulling performance is investigated. By generating wide and deep nulls toward and around the interference directions, the proposed method provides robustness against frequency ∞uctuation. Simulation results in realistic situations with frequency ∞uctuation are presented to illustrate the performance of the proposed technique. Comparisons with the standard fully adaptive nulling array are shown.

Intelligent Method for Designing Exact Orthogonal Blocking Matrix into Robust Wideband Beamformer Using Auxiliary Sensors

An innovative method for wideband adaptive beamforming is presented This method can allow large desired-direction error by generating a wide and deep null around the desired-direction at the blocking matrix output Moreover, it can provide good suppression performance for both directional and omni-directional interference and noise signals. Simulation results are included to illustrate the effectiveness of the proposed method.

Real-time implementation of an efficient RLS algorithm based on IIR filter for acoustic echo cancellation

An efficient acoustic echo canceller has been proposed for hands-free communication systems which use a recursive least squares (RLS) algorithm. It also employ an infinite impulse response (IIR) filter based on output error method. The proposed IIR-RLS filter is more suitable for modeling real systems due to its pole-zero structure and it is required fewer number of filter coefficients to identify the time-varying echo path as compared to the traditional FIR-NLMS filter. However, with non-stationary long durations signals the proposed IIR-RLS filter suffers from instability problem. To avoid this problem, auto covariance matrix resetting was employed. Furthermore, the proposed system has been implemented in real-time in a real environment using National Instruments NI-PXI-1042Q controller system and data acquisition input card PXI-4472. Practical results, show that the proposed algorithm has the local minimum solutions and remain stable.

Real-Time Implementation of New Adaptive Beamformer Sensor Array For Speech Enhancement in Hearing Aid

The objective of this paper is to provide improved real-time noise canceling performance while keeping the high quality of enhanced speech by using new robust adaptive beamformer. The proposed beamformer uses a new adaptive blocking matrix, which consists of linear prediction error filters (LPEFs). It also employ a multi-channel noise canceller with adaptive noise estimation filters (ANEFs) used for inverse modeling. The entire proposed system has been implemented in real-time in a real environment using National Instruments NI- PXI-1042Q controller system and data acquisition card NI-PXI-4472. Practical results show that the proposed beamformer produces results that are significantly favorable than standard GSC beamformer.